No! You could get a modded apk version of DQ for free character slot but then you won't be able to download from cloud. Not recommended at all or allowed. Just stick with what you got ofc.
Just buy the 0.99$ character slot. It really isn't that bad of a deal. It also lasts forever and less than a sandwich cost.
You can pay via Credit/Debit Card, Google Play credits from gift card or Google Opinion Rewards to gain free Google credits for easy character slot.
If you're a kid, you can even ask parents to help too.
Does it really hurt to pay for 1 character slot only for at least 1$ . You're supporting developers and this awesome game updating. This is why the game has gone so far. Also other paid stuff like vanities aka cosmetics and extra inventory.
If you're on apple , apple gift cards or their own rewards app.